Investigate fanning out multi-platform builds

[jonjohnsonjr]

I have a sneaking suspicion that it will be slower to try to do multiple go builds for the same target with different platforms due to build cache invalidation, but the go compiler might have improved since I last experimented with this.

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.